Load indicating washer

ABSTRACT

A load indicating washer, or tension washer, for visually indicating pre-determined magnitudes of tension force in a tension tie member. The tension washer comprises a body portion with a deformable, curved annular flange member depending from the body portion. When the tension washer is compressed against a flat bearing surface, the flange member deforms to produce a visual or color indication of the magnitude of load in the tie member.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. §119(e), this application claims the benefit ofU.S. Provisional Patent Application Ser. No. 61/930,819, filed on Jan.23, 2014, the entire contents of which are incorporated herein by thisreference.

BACKGROUND

(1) Field of Invention

This invention relates generally to a washer for use with a tension tiemember, where the washer provides a visual indication of the magnitudeof the tension force in the tie member.

(2) Background

Tension tie members are commonly used in building construction to pre-or post-tension beams, columns, walls, or other structural elements. Thetie members can be internal or external to the structural elements. Thetie members are connected to the structural elements in a manner thatapplying a tension force in the tie member will deliver a correspondingcompression force to the structural element. This compression forcepermits the structural element to resist an external load of a greatermagnitude than the same element could have carried without the tiemember installed.

Some types of construction techniques use materials that are difficultto consistently compress via tension tie members. For example, tensiontie members used in wood frame construction are typically tensioned by ahand-held tool or machine, and such devices can be difficult to controlor use. The resulting tension force in the tie members can vary greatlyfrom one tie member to another.

It is an object of the load indicating washer described herein toprovide a consistent and reliable visual indication of the magnitude oftension force in the tension tie member at the time of tie memberinstallation.

SUMMARY

The load indicating washer, or tension washer, has a body portiondefining a central bolt opening, and a deformable, curved annular flangemember depending from the body and having an outer edge. The top surfaceof the tension washer is a different color than the edge and bottomsurface of the washer. The edge and the bottom surface could be the samecolor or different colors. A threaded fastener, such as the mechanicaltensioner, is passed through the opening of the tension washer andtensioned by a socket or wrench applying torque to a nut or bolt head.As the threaded fastener is tensioned, the deformable flange member iscompressed against the flat bearing surface, thereby causing the flangemember to curl upward toward the socket, lifting the edge away from theflat bearing surface. This flange member curling action continues untilthe color of the edge or the bottom surface becomes visibile, therebyproviding a visual indicator that the requisite tension level has beenachieved in the fastener or mechanical tensioner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section showing a typical anchorage of the tie memberat the top of a structural wall.

FIG. 2 shows a top view and a cross section of the tension washer.

FIG. 3 is a plan view showing the tension washer connected to the flatbearing surface by a hexagonal bolt.

FIG. 4 is a cross section of the tension washer, spacing washer, andflat bearing surface, showing the proximate location of a typical hexbolt head.

FIG. 5 shows a nut connected to a tension end of a tie member andcompressing the tension washer against the flat bearing surface. Thetension washer and flat bearing surface are shown in cross section.

DETAILED DESCRIPTION

With reference to the drawings, the invention will now be described withregard for the best mode and the preferred embodiment. In general, thedevice disclosed herein is a load indicating washer, or tension washer,intended to provide a visual indication of a tension load in amechanical fastener. The embodiments disclosed herein are meant forillustration and not limitation of the invention.

The load indicating washer, or tension washer 50, is a device thatprovides a visual indication of a tension member reaching a certainmagnitude of tension load. For example, referring to FIG. 1, the tensionmember could be a tie member 15 used to retain a wall 23 of a structure,such as a house or light commercial building. Such tie members 15 can beused in a manner where a nut 25 threads onto a tension end 18 of the tiemember 15 and presses against a flat bearing surface 33, thereby causinga tension force in the tie member 15.

Referring to FIGS. 2-5, the tension washer 50 has a substantially planarbody portion 51 defining a central bolt opening 52, and a deformableannular flange member 53 depending from the body 51. The tension washer50 has a top surface 55, an edge 56, and a bottom surface 57. Thedeformable annular flange member 53 is curved from its base to the outeredge 56 such that the flange member 53 is concave upward toward the body51. The bottom surface 27 of the flange member is placed against a flatbearing surface 33, such as the bearing plate member or a flat washer orspacer 58, so that prior to loading the tension washer 50 the body 51 isseparated from the flat bearing surface 33 by a space 59.

A tension end 18 is passed through the opening 52 of the tension washer50 and tensioned by a socket or a wrench applying torque to a tensionadjustment device 25, such as a nut or bolt head. As the tie member 15is tensioned, such as by tightening the nut 25, the nut 25 exerts anincreasing compression load on the tension washer 50. Under thiscompression load, the flange member 53 is compressed against the flatbearing surface 33, thereby causing the flange member 53 to expandoutwardly by sliding along the flat bearing surface 33. During thisaction, the flange member 53 deforms by the edge 56 curling upwardtoward the nut 25 and away from the flat bearing surface 33 (See FIG.5). Plastic deformation can occur in the outer fibers of the flangemember 53 (the fibers along the bottom surface 27), thereby causingunrecoverable deformation and upward curling of the flange member 53. Asthe flange member 53 slides along the flat bearing surface 33 and curlsupward, the body 51 moves toward the flat bearing surface 33, therebyclosing the space 59. The flange member 53 thus has an unloaded shapeand a first deformed shape.

The tension washer 50 is placed by fitting the central opening 52 overthe tension end 18 of the tie member 15. Prior to loading, the annularflange 53 is in its unloaded shape, and the user sees only the topsurface 55 without the edge 56 or bottom surface 57 being visible. Asthe tie member 15 is tensioned and the tension washer 50 is compressedagainst the flat bearing surface 33, flange member 53 takes on its firstdeformed shape under a first compression load. In the first deformedshape, the edge 56 becomes visible when the magnitude of the tensionforce in the tie member 15 reaches a first magnitude. As further tensionis applied, the flange member 53 takes on a second deformed shape undera second compression load when the magnitude of the tension force in thetie member 15 reaches a second magnitude, where the first magnitude islower than the second magnitude. In the second deformed shape, theflange member 53 is severely curved, and the bottom surface 57 under theedge 56 becomes visible to the user. Thus, the edge 56 and the bottomsurface 57 provide a two-stage visual indication of tension magnitude inthe tie member 15 corresponding to the first deformed shape and thesecond deformed shape, respectively.

In one embodiment, the top surface 55 of the tension washer 50 is adifferent color than the edge 56 and bottom surface 57 of the washer 50.For example, the top surface 55 comprises a first color, and the edge 56and bottom surface 57 comprise a second color. The tension washer 50 isplaced on the tension end 18 and against the flat bearing surface 33.Prior to loading, the flange member 53 remains in its unloaded shape,and the user sees only the first color of the top surface 55 without thesecond color being visible. As the tension washer 50 is loaded, the edge56 curling action begins, and it continues to the first deformed shapeas described above, where the second color of the edge 56 or the bottomsurface 57 becomes visibile to the user. In this embodiment, thevisibility of the second color provides a one-stage visual indicatorthat a pre-determined magnitude of tension level has been achieved inthe tie member 15.

In another embodiment, the top surface 55, edge 56, and bottom surface57 comprise a first color, a second color, and a third color,respectively. As the tension washer 50 is loaded, the edge 56 curlingaction continues as described above until the flange member 53 reachesits first deformed shape and the second color of the edge 56 becomesvisible, thus indicating a first magnitude of tension force in the tiemember 15. As the tie member 15 is tensioned further, the edge 56curling action continues until the flange member 53 reaches its seconddeformed shape and the third color of the bottom surface 57 becomesvisibile to the user, thus providing a visual indication that a secondmagnitude of tension force has been reached in the tie member 15. Thefirst magnitude is lower than the second magnitude. The visibility ofthe second color and the third color provides a two-stage visualindicator corresponding to two different magnitudes of tension achievedin the tie member 15—the first magnitude and the second magnitude.

The tension washer 50 is comprised of metal, plastic, or some othermaterial that is capable of deforming properly under the requiredtension loads. In applications requiring a high tension force, thetension washer 50 comprises a material with a relatively high elasticmodulus, such as steel, so that the tension washer 50 does notprematurely deform. In applications requiring lighter tension loads, thetension washer 50 comprises material of a lower elastic modulus, such asdie cast metal or plastic, so that the tension washer 50 deformsproperly under the lighter load. In another embodiment, proper sizing ofthe annular flange member 53 is a manner of ensuring that the tensionmember 50 deforms properly under the required tension load. Thethickness of the annular flange member 53 is adjusted according to therequired tension load. The annular flange member 53 is either thickenedor thinned for larger or smaller tension loads, respectively. Also, thewidth of the annular flange member 53 can be made wider or more narrowas desired. The width of the flange member 53 affects its elasticity,with narrow flange members 53 being stiffer, and wider flange members 53being less stiff.

In another embodiment, the edge 56 curls away from the flat bearingsurface 33 until the edge 56 contacts the socket or wrench, therebyproviding a physical indication to the user that the threaded fasteneror mechanical tensioner 20 is properly tensioned.

The tension washer 50 can be used in a method of determining themagnitude of tension in the tension tie member 15 as follows. Thetension washer 50 of any of the foregoing embodiments is installed byplacing the central opening 52 over the tension end 18 of a tension tiemember 15 such that the bottom surface 57 is placed in contact with theflat bearing surface 33. The tension adjustment device 25 is threadedonto the tension end 18 of the tie member 15. The tension adjustmentdevice is adjusted to compress the tension washer 50 against the flatbearing surface 33 such that the annular flange member 53 begins todeform by curling upward toward the body portion 51, thereby causingseparation between the edge 56 of the flange member 53 and the flatbearing surface 33. The step of adjusting the tension adjustment devicecan be stopped when the edge becomes visible to the user, the bottomsurface becomes visible to the user, the first color becomes visible tothe user, or the second color becomes visible to the user. A firstmagnitude of tension force in the tie member 15 is identified andreached when the edge 56 becomes visible to the user, or when the firstcolor becomes visible to the user, as described above. Similarly, asecond magnitude of tension force in the tie member 15 is identified andreached when the bottom surface 57 or the second color becomes visibleto the user.

The foregoing embodiments are merely representative of the loadindicating washer device and not meant for limitation of the invention.For example, persons skilled in the art would readily appreciate thatthere are several embodiments and configurations of the annular flangemember that will not substantially alter the nature of the system.Likewise, elements and features of the disclosed embodiments could besubstituted or interchanged with elements and features of otherembodiments, as will be appreciated by an ordinary practitioner.Consequently, it is understood that equivalents and substitutions forcertain elements and components set forth above are part of the devicedescribed herein, and the true scope of the invention is set forth inthe claims below.

I claim:
 1. A tension washer for use with a tension tie member, thetension washer comprising: a body portion defining a central opening;and a deformable, curved annular flange member depending from the bodyportion and oriented concave upwardly toward the body portion, theflange member having an outer edge; wherein the tension washer has a topsurface and a bottom surface, and the bottom surface is adapted forplacement against a flat bearing surface; and wherein the flange memberis adapted to deform when compressed against the flat bearing surfacesuch that the shape of the deformed flange member comprises the edgespaced away from the flat bearing surface.
 2. The tension washer ofclaim 1, wherein: the annular flange member is adapted for a firstdeformed shape under a first compression load; and the edge in the firstdeformed shape is configured to provide a visual indication of the firstcompression load.
 3. The tension washer of claim 1, wherein: the annularflange member is adapted for a first deformed shape under a firstcompression load, and a second deformed shape under a second compressionload, said second compression load having a magnitude greater than thatof the first compression load; the edge of the first deformed shape isconfigured to provide a visual indication of the first compression load;and the bottom surface of the second deformed shape is configured toprovide a visual indication of the second compression load.
 4. Thetension washer of claim 1, wherein: the annular flange member is adaptedfor a first deformed shape under a first compression load; the topsurface comprises a first color and the edge comprises a second color;and the edge of the first deformed shape is configured such that thesecond color of the first deformed shape provides a visual indication ofthe first compression load.
 5. The tension washer of claim 1, wherein:the annular flange member is adapted for a first deformed shape under afirst compression load, and a second deformed shape under a secondcompression load, said second compression load having a magnitudegreater than that of the first compression load; the top surfacecomprises a first color, the edge comprises a second color, and thebottom surface comprises a third color; the edge of the first deformedshape is configured such that the second color of the first deformedshape provides a visual indication of the first compression load; andthe edge and the bottom surface of the first deformed shape areconfigured such that the second color and the third color of the seconddeformed shape provide a visual indication of the second compressionload.
 6. The tension washer of claim 1, wherein: the annular flangemember is adapted for a first deformed shape under a first compressionload; and the bottom surface of the first deformed shape is configuredto provide a visual indication of the first compression load.
 7. Thetension washer of claim 1, wherein: wherein the annular flange member isadapted for a first deformed shape under a first compression load; thetop surface comprises a first color and the bottom surface comprises asecond color; and the bottom surface of the first deformed shape isconfigured such that the second color in the first deformed shapeprovides a visual indication of the first compression load.
 8. A methodof determining the magnitude of tension in a tension tie member, saidmethod comprising the steps of: installing the tension washer of claim 1by placing the central opening over a tension end of a tension tiemember such that the bottom surface is placed in contact with the flatbearing surface; threading a tension adjustment device onto the tensionend of the tie member; adjusting the tension adjustment device tocompress the tension washer against the flat bearing surface such thatthe annular flange member begins to deform by curling upward toward thebody portion, thereby causing separation between the edge of the flangemember and the flat bearing surface.
 9. The method of claim 8, furthercomprising the step of stopping the adjusting of the tension adjustmentdevice when the edge becomes visible to the user.
 10. The method ofclaim 8, further comprising the step of stopping the adjusting of thetension adjustment device when the bottom surface becomes visible to theuser.
 11. The method of claim 8, further comprising the steps of:identifying a first magnitude of tension in the tie member when the edgebecomes visible to the user; and identifying a second magnitude oftension in the tie member when the bottom surface becomes visible to theuser.
 12. The method of claim 8, wherein the top surface comprises afirst color and the edge comprises a second color, said second color notvisible to the user prior to the step of adjusting the tensionadjustment device, the method further comprising the step of stoppingthe adjusting of the tension adjustment device when the second colorbecomes visible to the user.
 13. The method of claim 8, wherein the topsurface comprises a first color and the bottom surface comprises asecond color, said second color not visible to the user prior to thestep of adjusting the tension adjustment device, the method furthercomprising the step of stopping the adjusting of the tension adjustmentdevice when the second color becomes visible to the user.
 14. The methodof claim 8, wherein the top surface comprises a first color, the edgecomprises a second color, and the bottom surface comprises a thirdcolor, said second color and said third color not visible to the userprior to the step of adjusting the tension adjustment device, the methodfurther comprising the steps of: identifying a first magnitude oftension in the tie member when the first color becomes visible to theuser; and identifying a second magnitude of tension in the tie memberwhen the second color becomes visible to the user.